As described in U.S. Pat. No. 5,725,957, there are primarily two methods of reducing glare associated with surfaces of glass substrates. The first method involves depositing an “interference” coating stack on the glass substrate that controls glare by taking advantage of the optical interference within thin films. Such films usually have a thickness of about one-quarter or one-half the nominal wavelength of visible light, depending on the relative indexes of refraction of the coating and glass. The second method involves forming a light scattering, i.e. diffusing, means at the surface of the glass, usually either by altering the characteristics of the outermost surface of the glass substrate or via a diffuser coating on the glass substrate.
Interference coatings reduce glare without reducing resolution. However, they are relatively expensive to deposit, requiring the use of relatively high cost vacuum deposition techniques such as sputtering and precise manufacturing conditions, or very precise alkoxide solution dip coating techniques, with subsequent drying and firing. Strict thickness control and uniformity are required.
In attempting to reduce glare by diffusion of light, one approach has been to etch the outer surface of the glass substrate, or otherwise modify the outer surface of a coating deposited on the glass substrate. There are numerous drawbacks in etching or otherwise modifying the surface characteristics of a substrate or coated substrate. Etching by chemical means involves handling and storage of generally highly corrosive compounds (e.g. hydrofluoric acid). Such compounds create processing and disposal problems in view of increasingly stringent environmental laws. Etching by non-chemical means, such as by sandblasting, necessitates additional and costly processing operations. In U.S. Pat. No. 5,725,957, a transparent substrate is spray coated with a precursor solution formed by dissolving a precursor of an inorganic metal oxide in an organic solvent. As an alternative, another approach has been to incorporate diverse materials (e.g. mixed oxides having different refractive indexes) into coating compositions.
Although various approaches of reducing glare have been described, industry would find advantage in new approaches for providing an antiglare surface.